Bipolar - 4 wires - 4 phases ?

[DocBrown]

Hello

I have this bipolar stepper motor salvaged from an Epson Stylus Photo 925.
The service manual says it takes 42 Volts. Has 4 phases and 48 poles and 4 wires.
It is labled : EM-448 ; J74A2YFT .
I havn't found any datasheet of this thing. Though I guess it's a Mitsumi-kind-of.
1.) Now I thought bipolar stepper motors are always 2 phased ??
2.) 48 poles... does this mean the steps it takes for a full revolution or are there really only 24 steps/rev (4 phase / 2 = 2 phase --> 48 / 2 = 24). Or are there actually 96 steps ??

[MarkT]

They mean 2-phase - manufacturers often mistake phases for poles!

Its a bipolar motor, winding resistance 7ohms, inductance 10mH

We don't know the operating current though, so that's rather a guess.

Ignore the 42V for now, that's more a rough indication of the maximum speed the winding inductance allows.
If you connected a winding to 42V you would destroy the motor, its designed for constant-current chopper
drive such as the LB1946 mentioned.

We can guess the rough operating current by estimating the operating power from the weight of the motor.

As for the number of poles that could mean its a 192-step motor (bit unusual, 200 is the commonest count,
I'd readily believe that's a misprint - you could count the detents per revolution.